A solid electrolytic capacitor is produced by encapsulating a solid electrolytic capacitor element with a resin or the like. The solid electrolytic capacitor element comprises, for example, a laminate of an anode body, a dielectric layer, a semiconductor layer and a conductor layer in this order, in which the anode body is connected to a lead wire. The anode body is composed, for example, of a porous body obtained by compacting a valve action metal powder, and followed by sintering. The dielectric layer is composed, for example, of an insulating oxide thin layer obtained by anodizing the surface of the porous body. The semiconductor layer serves as a cathode relative to the anode body through the dielectric layer. The conductor layer is provided so as to facilitate electrical connection to the cathode. The conductor layer covers the periphery of the element, excluding the vicinity of the connection portion between the lead wire and the anode body. The cathode portion of the solid electrolytic capacitor element is composed of the semiconductor layer and the conductor layer.
The solid electrolytic capacitor element is laid on a cathode lead portion of a lead frame (hereinafter sometimes referred to simply as a “cathode lead”) and the conductor layer existing on the periphery of the element is electrically connected to the cathode lead. The cathode load is partially exposed on the outside of an outer packaging of the solid electrolytic capacitor to form a cathode terminal. On the other hand, the lead wire connected to the anode body (hereinafter sometimes referred to simply as an “anode lead wire”) is electrically connected to an anode lead portion of the lead frame (hereinafter sometimes referred to simply as a “anode lead”) and the anode lead is partially exposed on the outside of the outer packaging of the solid electrolytic capacitor to form an anode terminal.
A conductive adhesive such as adhesive silver paste is used so as to connect the solid electrolytic capacitor element to the cathode lead. Usually, the solid electrolytic capacitor element and the cathode lead are electrically connected so that conductive adhesive does not protrude from the connection surface of the solid electrolytic capacitor element and the cathode lead. When the conductive adhesive protrudes, it must be handled in the same manner as in the case using a solid electrolytic capacitor element with a large overall size, and therefore it is not preferred.
PLT 1 has proposed a solid electrolytic capacitor having high capacity and excellent high frequency property, in which a plurality of solid electrolytic capacitor elements are laid in parallel on a lead frame including a pair of opposing lead portions extending toward the inside of the frame. In this solid electrolytic capacitor, the plurality of solid electrolytic capacitor elements are laid adjacent to each other in parallel and encapsulated with an encapsulation resin material or the like. The encapsulation resin material usually has electrical insulating properties.
PLT 2 has proposed that a fixed layer extending between a plurality of solid electrolytic capacitor elements laid in proximity to each other in parallel is placed. The fixed layer placed so as to extend between solid electrolytic capacitor elements can prevent an encapsulation resin material from flowing into a gap between solid electrolytic capacitor elements. Thus, it is made possible to obtain a chip-shaped solid electrolytic capacitor which has low equivalent series resistance and low leakage current. Air remains in the gap between solid electrolytic capacitor elements. Air has electrical insulating properties.
PLT 3 discloses a solid electrolytic capacitor in which solid electrolytic capacitor elements are not laid adjacent to each other, but the solid electrolytic capacitor elements are laid by intentionally increasing a gap therebetween so that an encapsulation resin material positively flows into the gap. The encapsulation resin material usually has electrical insulating properties. PLT 3 describes that it is possible to prevent large deterioration of equivalent series resistance (ESR), leakage current (LC) and the like in a durability test of allowing to stand in the environment maintained at a temperature of 60° C. and a relative humidity of 90 to 95% for a long time as the encapsulation resin material flowed positively serves as a cushion.
PLT 4 describes that a solid electrolytic capacitor, which scarcely exhibits an increase in a leakage current even when heat shock or the like, due to solder heat is applied, is obtained by adjusting the proportion of air in a gap between adjacent solid electrolytic capacitor elements to 60 volume % or less. In order to remove air from the gap between solid electrolytic capacitor elements, a resin or an oily substance is absorbed in the gap. PLT 4 teaches that the resin or oily substance preferably has electrical insulating properties.